Effects of insulin-like growth factor-I on follicle growth, oocyte maturation, and ovarian steroidogenesis and plasminogen activator activity in the rabbit

Yasunori Yoshimura, Motomu Ando, Shinya Nagamatsu, Mitsutoshi Iwashita, Tomoko Adachi, Kou Sueoka, Toyohiko Miyazaki, Naoaki Kuji, Mamoru Tanaka

Research output: Contribution to journalArticlepeer-review

66 Citations (Scopus)

Abstract

We examined the effects of insulin-like growth factor (IGF)-I on follicular growth, oocyte maturation, and ovarian steroidogenesis and plasminogen activator (PA) activity in vitro, using a perfused rabbit ovary preparation in order to determine whether the follicle-stimulating effects of growth hormone (GH) are mediated by IGF-I. The addition of IGF-I to the perfusate stimulated follicular growth and the resumption of meiosis in follicular oocytes in a dose-dependent manner. There was no significant difference in the production of progesterone by perfused rabbit ovaries between IGF-I-treated and control ovaries, whereas IGF-I increased the production of estradiol (E2) by perfused rabbit ovaries in a dose-dependent manner. The concomitant addition of a monoclonal antibody recognizing the type I IGF receptor, αIR-3, to the perfusate significantly blocked IGFI- stimulated follicular growth, oocyte maturation, and E2 production. Intrafollicular PA activity increased significantly 4 h after exposure to 10 or 100 ng/ml of IGF-I and reached maximal levels at 6 h. The percentage increase in follicle diameter at 6 h after exposure to IGF-I was significantly correlated with the intrafollicular PA activity. Treatment with GH resulted in a 2.7fold increase in intrafollicular levels of IGF-I mRNA. The binding of [125I]-IGF-1 to rabbit ovarian membrane preparations was inhibited by unlabeled 1GF-I and IGF-II in a concentration-dependent manner. The relative affinity of the IGF-I receptor for IGFI, IGF-II, and insulin was typical of type I binding (IGF-I > IGFII > insulin). Affinity cross-linking of ovarian membranes with [125I]-IGF-I revealed a radiolabeled band corresponding to a molecular weight of 135 000, the α subunit of the type I IGF receptor. This band was totally displaced by IGF-I and αIR-3. It was concluded that IGF-I stimulated follicular development, E2 production, and oocyte maturation by interacting with its specific receptor located in rabbit ovarian membranes.

Original languageEnglish
Pages (from-to)152-160
Number of pages9
JournalBiology of reproduction
Volume55
Issue number1
DOIs
Publication statusPublished - 1996 Jul

ASJC Scopus subject areas

  • Reproductive Medicine
  • Cell Biology

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